Headlamp



June 4, 1935.

R. N. FALGE ET AL HEADLAMP Filed April 26, 1953 5 Sheets-Sheet 1 gmnnliofd 0 foizz/ jig/576% flea r! 5023/ 4%? M-%% June 4, 1935. N. F'ALGE' ET AL HEADLAMP Filed April 26, 1933 5 Sheets-Sheet 2 Faled$ ggy/7 fizz, W

June 4, 1935. R N, FALGE ET AL 2,003,805

HEADLAMP Fi1ed April 26, 1933 s Sheets-Sheet 5 gwucntob filez/ W554 & .1741/11 TFazZ/g/ June 4, 1935. R, AL ET AL 2,003,805

HEADLAMP Filed April 26, 1953 5 sheets-sheet 4 Jwumtou filed 21541 71 x JGdI/l) MF%@Q Patented June 4, 1935 UNITED STATES PATENT OFFICE HEADLAIVIP Application April 26, 1933, Serial No. 667,958 3 Claims. (01. 240-414) This invention is a continuation in part of our prior application Patent No. 1,929,111, granted October 3, 1922. In that patent there is disclosed, among other things, a headlighting sys- 5 tom in whichone of the lamps, preferably the right headlamp, illuminates the full width of the road, while the left headlamp illuminates only the right hand side of the road. Both lamps are designed to provide a high beam, an intermediate beam, and a low beam. By so operating the lamps that a lower beam is projectedv from the right headlamp than from the left headlamp an asymmetrical composite beam pattern is obtained which is lower on the left side than onv the right side. This pattern is especially desirable in that it relieves the driver of an approaching car from glare, but at the same time provides illumination far down the road on the right hand side, and directly in front of the car, giving increased safety 20 during the period of passing.

The present invention has to do with a design of the headlamp which casts a beam on but one side of the road as described above. Obviously, a lamp of this designmay be used oneither side of the car, as preferred, but in the system described in our prior patent it is preferably located on the left side.

The light directing means of the headlamp is characterized by proper formation of the refiector or lens, or both, to provide a plurality of beams and to direct those beams toward one side of the road. This last is accomplished by the provision of unsymmetrical or fractional flutes.

In this type of lighting system it is essential that 35 there shall be a fairly sharp and definite cutoff at the left edge of the beam which is directed toward the right side of the road so that the high intensity will not be directed into the eyes of an approaching driver. We have accomplished this object by designing the flutes so that in spite of manufacturing variations in the location of filaments in the bulb, or in the location of the bulb in the lamp, etc., there will be substantially no light thrown to the left of the vertical plane through the axis of the lamp straight ahead of the car.

Another important feature in our design consists in providing flutes of greater spread over the top and bottom zones of the light directing means than over the central zone. The object of this is to concentrate light at the upper left hand corner of the beam to give a hot spot down the right side of the road where the best illumination is needed in passing.

In the. drawings:

Figure 1 is a vertical section through a lamp embodying oneform of our invention.

Figure 2 is a front view of the lamp in Figure 1.

Figures 3, 4 and 5 are horizontal sections on the 5 corresponding lines of Figure 2.

Figure 6 is a vertical section corresponding to Figure 1 showing a further modification.

Figure 7 is a front view, and Figure 8 a rear view of the lens shown in Figure 6. 10

Figure 9 is a front elevation of a modified form of light directing means in the form of a special reflector.

Figures 10, 11 and 12 are sections on the corresponding lines of Figure 10. 5

Figures 13, 14 and 15 illustrate the beam pattern produced by the intermediate filament, the upper filament, and lower filament respectively. Figure 16 is a section taken on line lE-IG of Figure 8. The view illustrates somewhat diagrammatically the principle of design whereby lateral insensitivity is achieved.

Figure 17 is a section through a conventional concave full flute.

Each of the designs of light directing means herein disclosed is characterized by the provision of a plurality of transversely extending superimposed zones or areas, preferably three. These include a top zone I, an intermediate zone 2, and a lower zone 3. The top and bottom zones are 3 designed to direct light below the light from the intermediate zone so that the latter forms the top of the beam and upon shifting to a higher light source, the top of the beam is dropped.

In Figures 1 to 5, we have illustrated our invention embodied in a combination of special reflector and lens. The reflector is illustrated in Figure 1. The upper half of the reflector has its focal point at 5, slightly to the rear of the light sources, while the lower half of the reflector has its focal point at 6, slightly in front of the light sources. The top zone I, and the bottom zone 3 of the reflector, are tilted downwardly to depress the corresponding light rays below the light from the intermediate zone. This is made clear by a 5 comparison of the outline of corresponding parts of the reflector with the dotted line outline of the corresponding portions of a true parabola.

We have shown the lamp. provided with a V- shaped filament I2 lying along the lamp axis and between the two focal points, and with a V-shaped lament It below the filament i2 and a linear inclined filament it above the filament l2.

With this arrangement the filament ID will pro- Vide the highest beam. This beam will have its Cir cutoff above the usual high beam provided in conventional two-beam headlamps. The filament I2 will project the conventional high beam, while the filament M will project a somewhat lower beam. If preferred, all three filaments may be of conventional V-shape.

Over the reflector we have placed a lens provided with asymmetrical flutes to confine the light to the right side of the road. As shown in Figures 3 and 5 the flutes I6 over the top and bottom zones are designed to spread the light to a greater extent than the flutes over the intermediate zone. This is accomplished by giving them greater curvature. center of the intermediate zone are likewise of greater curvature than the flutes 20 over the sides of the intermediate zone. The purpose of this is to concentrate the light from the sides of the intermediate zone at the top left-hand corner of the beam as illustrated by the concentrated portions 20' of the beam pattern shown in Figures 13 to 15. i

Of the remainder of the beam patterns, the widest spread portion I6 is produced by the top and bottom zones, and the portion l8 of intermediate spread is produced by the center of the intermediate zone.

In Figures 6, '7 and 8 we have illustrated our invention embodied in a headlamp comprising a plain parabolic reflector 23 equipped with a lens 25 having relatively strong down-bending prisms 21 over the top and bottom zones and shallower prisms 29 over the center of the intermediate zone. The prisms 3| over the sides of the intermediate zone are of even less angle to concentrate the light at the upper left hand corner of the beam pattern. This arrangement will produce beam patterns very similar to those previously described. It has advantages in manufacture in that a simple type of reflector may be used. It will, of course, produce a somewhat different distribution of light within the beam patterns because of the difference in reflector design.

All of the half flutes are preferably designed and arranged to render the beam insensitive at its left boundary to variations in filament position. In other Words, while the lamp is already insensitive to changes in filament positioning to the extent that the proper degree of tilt between beams and satisfactory distribution of light in the beam is obtained even though the filament be as much as .060" out of position in any direction in the vertical plane-this being accomplished by the reflector design previously described,by proper .design of the half flutes we have succeeded in causing the left side of the beam to terminate in a substantially vertical plane through the reflector axis regardless of variation in filament position in any direction within the same limits. This is important in that it enables the headlamp adjuster at the service station to normally encountered in service.

To simplify the discussion let us consider the fractional flute as composed of a full flute superimposed on a prism. Let us consider individually The flutes l8 over the.

each of the elements which contribute to the net prismatic correction.

Let us confine our attention first to a parabolic reflector with the light source at focus.

Prismatic effect is needed to offset the spreading effect of the flutes. The prismatic effect required is one-half. the spreading effect of the flute. In conventional designs where the spreading eifect increases from the two sides towards the center, the prismatic effect increases in similar manner.

Prismatic effect is needed to correct for lateral spread due to filament size. The compensation in this case increases progressively from both sides towards the center of the lens, as the distance from the light source to the reflector decreases.

Prismatic effect is needed to correct for commercial inaccuracies in filament placement. Inaccuracies usually considered are 0.060 in any direction.

Lateral deflection of rays, due to vertical inaccuracies in filament placement, is negligible and will be disregarded.

Prismatic effect is needed to correct for inaccuracies in filament placement behind the focus. Correction is limited to the left side of the reflector since rays from that side only are deflected to the left. Rays from the center are deflected more for a given filament displacement than are rays from the two sides. Prismatic effect must, therefore, increase progressively from the left side toward the center.

Prismatic effect is needed to correct for inaccuracies in filament placement ahead of the focus. Correction is limited to the right side of the reflector since rays from that side only are deflected to the left. Rays from the center are deflected more for a given filament displacement than are rays from the two sides. Prismatic effect must, therefore, increase progressively from the right side toward the center.

Consequently, prismatic effect needed to correct for axial displacement of the light source 7 increases progressively from the two sides of the lens towards the center.

' Prismatic effect is needed to correct for sideways inaccuracies in filament placement. When the filament is displaced to the left, rays from points 'on the reflector ahead of the focal plane only are deflected to the left, and by progressively increasing amounts from the focal plane towards both sides. When the filament is displaced to the right, rays from points on the reflector behind the focal plane only are displaced to the left by progressively increasing amounts from the focal plane toward the center.

Consequently, prismatic effect needed to compensate for sideways inaccuracies in filament placement decreases progressively from both sides to the focal plane and then increases towards the center.

From this it appears that for a parabolic reflector covered by a lens with flutes of uniform spread or decreasing spread towards both sides, all factors tend to progressively increase the prismatic effect from the focal plane towards the center. Outside the focal plane, the tendency is the same except for movement of. the filament towards the left. The effect of the latter is relatively small so that we may conclude that the general tendency in a headlamp incorporating a parabolic reflector and conventional two-beam lens is that of progressively increasing prismatic correction from the two sides towards the center.

We have applied this principle in the design of the half flutes as shown in Figure 16. We have chosen for the left boundary of the beams, rays of light from the extreme side portions of the reflector. The flutes over these portions of the reflector may be designed with little or no prismatic action at their left extremities. The prismatic action at the left side of the half flutes increases as the vertical center line of the lamp is approached. As a consequence, going from the side of the lamp to the center line, the leftmost ray of each successive flute is thrown a little more to the right, providing a tolerance so that even if the filament is .060" out of position, still no ray will pass to the left of the vertical center line of the lamp.

This result is accomplished by the design of half flutes shown in Figure 16. The principle of the design is illustrated in Figure 1'7. Considering the full flute 22 it will be noted that a ray 24 passing through the glass on the center line of the flute is unchanged in direction for at this point the opposite faces of the glass are parallel. Rays striking the glass to the right of the center line are directed to the right. The greater the distance from the center, the greater the degree of bending. If it is desired that the leftmost ray from the half. flute shall be unchanged in its direction the center line of the flute should be its left boundary. If it is desired that the leftmost ray from a half flute should be deflected to the right, the half flute should terminate to the right of the center line. The farther to the right one wants to deflect the leftmost ray, the farther to the right of the center line should the left boundary of the half flute be. Conversely if it is desired that the leftmost ray from the flute should be deflected to the left, the left boundary of. the flute should extend to the left of the center line.

In Figure 16 the distance from the left boundary line of the fractional flute to the flute center line indicated at F increases as the vertical center line of the lamp is approached. One method of determining the amount of this increase is to design the flutes so that the leftmost ray from each flute is parallel with the vertical plane through the longitudinal center line of the car for that position of the filament within the 0.060" tolerance allowed which directs the leftmost ray farthest to the left.

This effect is modified by variation in radius of curvature of the flutes in different parts of the lens to get the desired distribution of light in the beam.

We have chosen to use concave half flutes for the reason that with this shape the side of the flute that determines the left margin of the beam can be more accurately molded than with convex flutes for a sharper corner is obtained by the impress of the plunger as in the production of a concave flute than by the flow of the glass into the recess.

With the described arrangement the left cutoff of the beam patterns shown in Figures 13 to 15 will be fairly definite so that the approaching driver will not be subjected to glare.

In Figures 9 to 12 we have shown our invention embodied in the reflector alone. The reflector may be of the construction shown in Figure 1, except that half flutes are formed in the reflector to spread the light. These flutes are shaped to perform the same functions as the flutes in the lenses previously described. Thus the flutes nearer the center of the lamp are designed with cutoffs farther to the right of the flute center line so as to give lateral insensitivity. The flutes 32 at top and bottom are wider than those on intermediate zone to give greater lateral spread to the rays from these portions. The same result may be accomplished by giving greater or less transverse curvature of the flutes.

Our light directing means is capable of considerable modification in practice. Thus instead of doing all of the downward bending in the reflector or lens, part may be done in the reflector, and part in the lens. The same is true in the case 'of the sidewise bending or spreading of the light. If preferred, convex flutes may be employed instead of concave flutes, and in such event the same principle of design would be employed to render them insensitive to variations in lateral position of the light source. It is likewise obvious that in place of using a number of filaments one light source may be shifted to the various positions in the reflector. Other modifications will occur to those skilled in the art.

In the case of the down-bending, part of the bending may be done by tilting the reflector and part by the use of prisms on the lens. The same variations may be resorted toin the case of the side-bending of rays. Thus full flutes may be used on the reflector in combination with sidebending prisms on the lens; or the intermediate section of the reflector may be turned to throw light to one side of the road and the light may be spread by means of full flutes on the lens. These variations arise from the fact that as pointed out in our original case, a fractional flute is really a combination of full flute and prism, in other words, a device for spreading light and a device for bending light in one direction.

We claim:

1. A lens including top, bottom and intermediate portions, the intermediate portion including side and center portions, said top and bottom portions being provided with down-bending prisms, and said center portion being provided with down-bending prisms of less bending power than the first-named prisms, said lens being provided with vertically extending half flutes in which the prismatic action at one margin of each of the flutes increases as the center line of the lamp is approached.

2. In a headlamp, light distributing means including three transversely extending superim-' posed zones extending from one side to the other thereof, the upper and lower zones being constructed to depress light downwardly, said light distributing means being provided with fractional flutes for distributing light toward one side of the road only, the flutes over the intermediate zone being of less spread than the flutes over the upper and lower zones, the flutes over the center of the intermediate zone being of greater spread than the flutes over the sides of the intermediate zone.

3. In a headlamp, light distributing means including a plurality of transversely extending superimposed zones extending from one side to the other thereof, one of said zones being provided with asymmetrical flutes for spreading light to one side of the road only, the light deflecting action at one margin of each of the flutes increasing as the center line of the lamp is approached.

ROBERT N. FALGE. CHARLES E. GODLEY. 

